I've used a ~teaspoon of CarbonKiller with water for ~30 cases at a time.
But I find the same result as with dunking after lead dip annealing. The cases have to be dried inside & out(not just blown out), then coated, or they'll tarnish within a week. Checked em with a borescope..
Look with a magnifier.

The carbon inside the case, and the thin coating of case lube, or polish on the outside, act to prevent tarnishing. Then we go & remove that for some reason...
Well, put it back, or your brass will oxidize.
Does it matter?
Well, we're expending energy here to CLEAN our brass, not tarnish it.

There is another issue that should be accounted for with necks so clean; bullet galling.
Carbon works just fine to seperate the copper in your brass from your bullet jackets.
I coat bullets anyway, and many lube necks, but neither is needed -unless you ultrasonically clean the necks.

The fella that doesn't clean his brass at all is probably miles ahead of us.

There is another issue that should be accounted for with necks so clean; bullet galling.
Carbon works just fine to separate the copper in your brass from your bullet jackets.
I coat bullets anyway, and many lube necks, but neither is needed -unless you ultrasonically clean the necks.

The fella that doesn't clean his brass at all is probably miles ahead of us.

I pretty much agree. Especially with the ultrasonic-cleaned necks. Bullet friction/tension with the US cleaned case necks was much different. I noted this so much right off the bat while seating bullets that the first thing I did at the range was compare the US cleaned reloads (with the squeaky clean case necks) POIs to identical reloads with cases that were carbon-fouled (no US cleaned). You guessed it. There was a 1 1/2" to 2" difference in the POIs at 295 yds.

As a consequence, on the cases that I've already US cleaned, I now lube the case necks with Imperial Resizing Wax and then remove as much of the Was as possible with dry Q-Tip ear cleaners prior to seating the bullets. This still leaves a light coating of the Imperial Case Lube in the case necks, and the resistance to bullet seating is pretty similar to my carbon-fouled cases. The POI and MV is now the same with these US-cleaned cases, as with the carbon-fouled ones.

Good points that you've made. My experiences with US cleaning lead me to very similar conclusions. I never did anything to formally clean my cases for decades - such as vibratory or tumble cleaning them. Like you say, now that I've US cleaned some brass, it seems like not cleaning them served me very well - maybe even put me ahead in this game/hobby.

I clean my necks, inside & out, with 0000 steel wool and load the cases. It rarely seems necessary to clean the cases themselves. What are you guys doing to get your cases dirty?

I shoot mine.

Carbon deposits...not so much dirt dirty though.........
I'm currently in the ultrasonics camp, but I swing back and forth. I enjoyed SS media in a tumblers, but am concerned with case hardening. Maybe I need one of those really cool annealing machines?

Scott

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I make some of the finest writing instruments available. My favorite is the Cartridge Pen and closely followed by Fountain/Rollerballs.....

I used to tumble cases, but stopped doing that years ago. Now I simply twist a hunk of 0000 steel wool around outside of necks, and clean inside of necks with a nylon brush dipped in denatured alcohol.

The advantage of US cleaners supposedly is that they clean inside the case.

At least it's all in one place, years ago when this stuff first came around you had to go here and there(run-around-ish) to get everything you needed. I still don't use the LemiShine(can't find it locally).
There is also a few videos on YTube that show it in use....

Give it a try, judge for yourself.....
Scott

__________________
I make some of the finest writing instruments available. My favorite is the Cartridge Pen and closely followed by Fountain/Rollerballs.....